(i) Technical Field
A certain aspect of the embodiments discussed herein is related to a semiconductor device. Another aspect of the embodiments is related to a semiconductor device having a SiC substrate.
(ii) Related Art
A semiconductor devices using a nitride semiconductor is used as a power device operating at high frequencies and outputting high power. Particularly, there is known an FET such as a high electron mobility transistor (HEMT) as a semiconductor device suitable for amplification in a high-frequency or RF (radio frequency) band such as a microwave band, a quasi-millimeter band or a millimeter band.
As a semiconductor device having a nitride semiconductor, there is known a semiconductor device in which an AlN layer, an AlGaN layer, a GaN layer and an electron supply layer are sequentially stacked in this order on a Si substrate (see Japanese Patent application Publication No. 2008-166349). Besides the Si substrate, there is known a SiC substrate having a lattice constant relatively close to that of GaN as a substrate for the semiconductor device including a nitride semiconductor.
The semiconductor device using a nitride semiconductor is desired to operate at higher frequencies. To achieve higher operating frequencies, it is desired to improve the pinch-off characteristic by a short gate.